In principle, counter track joints of the above-mentioned type are known from U.S. Pat. No. 6,848,999 showing joints with 6 balls and with 8 balls. The type of ball tracks described here corresponds to the type known in itself from Rzeppa joints (RF joints) and undercut-free joints (UF joints). This means that the center lines of the ball tracks consist of uniform radii (RF joints) and, respectively, are composed of radii and adjoining axis-parallel straight lines (UF joints). In the counter track joints described, the axial opening direction of the pairs of tracks alternates around the circumference, which leads to the type of counter track joint. Counter track joints of this type are disadvantageous in that the angle of articulation is limited to approximately 45 degrees because when this angle of articulation is exceeded, the first ball in the joint articulation plane leaves the first pairs of track.
From DE 103 37 612 A1 there are known counter track joints wherein the track center lines of the first pairs of tracks whose opening angle—when the joint is in the aligned condition—points towards the joint base, are designed in such a way that, when the joint is articulated, the opening angle, from a certain angle of articulation onwards, experiences a reversal of its direction of opening. More particularly, this is achieved in that the center lines of the ball tracks of the first pairs of tracks are S-shaped and thus each comprise a turning point.
U.S. Publication No. 2004/116192, inter alia, describes counter track joints wherein the center lines of the first outer ball tracks comprise a turning point near the joint aperture, so that the center lines of the first outer ball tracks are S-shaped. Because of the requirement of symmetry, the same applies to the center lines of the first inner ball tracks of the inner joint part. The angle of articulation of said counter track joints can be increased in this way.
As far as joints of the two latter types are concerned, the basic principle of counter track joints, i.e. atlernately opposed directions of the track opening angles and thus alternately opposed directions of the axial forces of balls acting on the ball cage only applies until a ball has reached the turning point from the inwardly curved track region to the outwardly curved track region. When the angle of articulation at which the ball occupies said second track region of the respective S-shaped tracks has been reached, the track opening angles are no longer, in their entirety, alternately directed around the circumference and the axial forces applied by the balls to the ball cage are no longer axially balanced. The counter track principle thus no longer applies and the ball cage has to axially support itself at the outer joint part and/or on the ball hub. Because of the increased internal friction between the ball cage and the outer joint part and inner joint part respectively, this can lead to a reduced service life.